"I'm asking you very seriously to become much more active," Gore told researchers gathered here for the American Geophysical Union's fall meeting, the world's largest scientific meeting. Some 15,000 scientists are at the conference; more than one-third filled two giant ballrooms at the Marriott Hotel to capacity hear him talk.
"Get involved," he said, "because so much is at stake."
Gore's documentary, "An Inconvenient Truth," popularized the significant -- and increasingly catastrophic -- changes under way on Earth as a result of human activity. Gore's evidence came largely from those sitting in the audience: Researchers studying Antarctic ice cores, ocean sediments, Arctic sea ice, clouds, mountain glaciers and a host of different planetary systems.
Their most recent evidence, unveiled in the past week, suggests the pace and scope of change surpasses even what scientists suspected a year ago.
-- The Antarctic ice core record, for example, now extends back to 800,000 years. Yet scientists studying that record warn that current trends render moot any comparison with information locked in ice: The planet, they say, is warming to a degree unseen in 40 million years, as the first mammals were evolving. Sea sediments bolster that hypothesis.
-- Arctic ice could be gone in the summer within 34 years.
That's decades earlier than previously thought, and it rids the Northern Hemisphere of its refrigerator. And "if we allow it to go," Gore said, "it won't come back on any time scale relevant to the human species."
For Gore, the climate crisis is a symptom -- "the most prominent and dangerous symptom" -- of a larger ailment: Humanity's relationship with the planet.
"We have somehow persuaded ourselves that we really don't have to care that much about what we're doing to future generations," he said.
"We have to find a way to communicate the direness of the situation."
James Hansen, director of NASA'S Goddard Institute for Space Studies, had a front row seat to Gore's hour-long talk. His name often comes up when talk turns to the need in science for a standard-bearer; more than any scientist, he has generated headlines for his spars with the White House on climate change.
He agreed fully with Gore's call. "Scientists have not done a good job communicating with the public," he said in an interview.
The "huge gap" between where the science is and what the public knows, Hansen added, "is partly our fault and part of the problem."
Dan Kammen, co-director of the University of California's Institute of the Environment and a professor in the Energy and Resources Group, said being a scientist activist has its price. He's lost out on grants because of his political positions on energy and climate issues, he said.
"Some of us have been doing this for some time and at some risk," Kammen said.
Are more scientists likely to heed Gore's call? In a few weeks, a pack of climate scientists and politicians are planning a demonstration in front of the White House.
"There is a lot of frustration" with inaction on curbing carbon emissions, Kammen said. "But science is inherently a discipline of skepticism."
But rare is the scientist who can pack so many colleagues into two ballrooms that, as happened Thursday, organizers must turn people away at the door.
Jerry Porter, an atmospheric scientist at the Lawrence Livermore National Laboratory, could only shake his head in wonder at Gore's grasp of the underlying science and its implications.
"He's a deeper thinker about environmental issues than those of us in the environmental sciences," he said.
Contact Douglas Fischer at firstname.lastname@example.org or (510) 208-6425.